Cable ties generally comprise an elongate strap, commonly of a plastics material, and a head having an aperture extending through the head. The head is usually, but not necessarily formed integrally with the strap at one end thereof. The head includes a means for engaging the strap which allows the free end of the strap to be inserted into the head aperture to form a loop, and pulled through to reduce the loop size, but prevents the strap from being pulled in a reverse direction to expand the loop size.
Cable ties are known in which the head and strap engaging means are molded in one piece. This arrangement eases manufacture, but imposes a strength limitation because the engaging means, commonly a pawl, is of a plastics material. For applications requiring high strength, it has been proposed to use a metal barb extending into the head aperture at an angle to allow sliding movement of the strap in one direction only. The metal barb is embedded in the material of the head.
A cable tie with a metal barb is described in U.S. Pat. No. 3,408,699, in which a barb, referred to as prior art, is shown as having a generally rectangular body with a knife edge formed at on end thereof. The barb of the preferred embodiments of U.S. Pat. No. 3,408,699 is described as having a weakened area along a line about which the barb is to flex during and after insertion of the strap into the head aperture. Reducing the force needed to flex the barb reduces the force needed to insert and pull the strap through the aperture. It is stated that weakening can be achieved in a number of ways, including removal of material from the barb in its flexure region, making the barb thinner at or adjacent its flexure region, or by chemical treatment or annealing. With regard to the possibility of removing material from the barb at its flexure region, U.S. Pat. No. 3,408,699 shows a barb having a hole cut out of it in the region where flexure is to take place, but a possibility is indicated that the sides of the barb may tapered below the flexure line or that two holes (rather than one) may be placed at the edge or anywhere along the flexure line.